In the last year we have isolated and identified a new and potent mineralocorticoid, 19-nor-deoxycorticosterone from the urine of rats with adrenal regeneration hypertension. We propose to look for and demonstrate the existence of this steroid in the human and develop a radioimmunoassay to measure it in urine and plasma and study its role, if any, in human low renin hypertension. In addition, the regulation of the secretion will be studied by measuring 19-nor-DOC after the administration of ACTH, dexamethasone, and metopyrone and after ingesting a low and high sodium diet. The other aspect of this study includes the search for unknown mineralocorticoids in the urine of patients with low renin hypertension employing identical technology developed during the detection, purification, and elucidation of the structure of 19-nor-DOC. We have already detected the existence of another yet unidentified sodium-retaining steroid in the urine of a patient with low renin hypertension.